Revert cdcf58e5 "[RISCV] enable LTO support, pass some options to linker."

This started passing target-features on the linker line, not just for RISCV but
for all targets, leading to error messages in Chromium Android build:

  '+soft-float-abi' is not a recognized feature for this target (ignoring feature)
  '+soft-float-abi' is not a recognized feature for this target (ignoring feature)

See Phabricator review for details.

Reverting until this can be fixed properly.

> Summary:
> 1. enable LTO need to pass target feature and abi to LTO code generation
>    RISCV backend need the target feature to decide which extension used in
>    code generation.
> 2. move getTargetFeatures to CommonArgs.h and add ForLTOPlugin flag
> 3. add general tools::getTargetABI in CommonArgs.h because different target uses different
>    way to get the target ABI.
>
> Patch by Kuan Hsu Chen (khchen)
>
> Reviewers: lenary, lewis-revill, asb, MaskRay
>
> Reviewed By: lenary
>
> Subscribers: hiraditya, dschuff, aheejin, fedor.sergeev, mehdi_amini, inglorion, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, kito-cheng, shiva0217, jrtc27, MaskRay, zzheng, edward-jones, steven_wu, rogfer01, MartinMosbeck, brucehoult, the_o, dexonsmith, rkruppe, PkmX, jocewei, psnobl, benna, Jim, lenary, s.egerton, pzheng, cfe-commits
>
> Tags: #clang
>
> Differential Revision: https://reviews.llvm.org/D67409